Larger data processing systems typically include a plurality of host processors and typically require storage for large numbers of data storage media. The data storage media are typically optical disks or magnetic tapes which are stored in a library having a plurality of storage slots, and which can be accessed by a picker. The storage slots are typically arranged in rows, and the rows are arranged in columns. The picker is typically a robotic device which moves along a guideway in an X-Y, or rotary motion to access the various storage slots.
Often, one such library has insufficient storage capacity, and simply adding capacity would make the library response too slow. Therefore, another library may be added to the system. The load balancing between libraries is difficult, and, in many instances, it is desirable to move many of the data storage media from one of the libraries to the other so that the workload may be balanced. The problem becomes more pronounced when still more libraries are in the system.
Conventional pass through systems for automated libraries typically require the libraries to be specially designed to have a common wall and allow for the insertion of a small number of data storage media into slots in the common wall by one library while the other library accesses the data storage media from the slots in the common wall.
Additionally, it may be desirable to load or to unload large quantities of data storage media into or out of a library.
Conventional input/output slots are separate from any pass through slots and provide an access to the library which may pivot or slide between an interior position accessible by the library picker and an exterior position accessible by an operator. The conventional input/output slots tend to allow loading and unloading of only small quantities of data storage media.